Does it not have a recovery partion - What is the model ?
Try this
- Copy all your files and documents to an external storage device. Using Reatogo
- Shut down the computer.
- Turn the PC back on and hit the F8 key repeatedly until the Advanced Boot Option Screen appears.
- Click “Repair Your Computer” if you are not already on it and then press ENTER
- choose your country and click OK
- On the “System Recovery Options Screen” click “Restore Application” which is the last option.
- Follow the on-screen instructions
- When prompted, click on “Full Factory Recovery”
- “Next”
- Click “Yes”
- you will notice for a while it seems like nothing is happening, give it some time.
- After some minutes, recovery will complete and you click “Finish”
Or this
- Press and hold the 0 (zero) key and at the same time, tap the power button once to switch on your notebook.
- When the machine Starts beeping; release the 0 key.
- When prompted by the warning screen; select Yes to continue with the system recovery.
- Select Recovery of Factory Default Software; click Next.
- Select Recover to out-of-box state. Click Next again.
- Click Next to Start recovery.